update the doc of gluten usage (oap-project#150)

docs/ArrowInstallation.md

@@ -40,9 +40,9 @@ make install
 # build java
 cd ../../java
 # change property 'arrow.cpp.build.dir' to the relative path of cpp build dir in gandiva/pom.xml
-mvn clean install -P arrow-jni -am -Darrow.cpp.build.dir=../cpp/release-build/release/ -DskipTests -Dcheckstyle.skip
+mvn clean install -P arrow-jni -am -Darrow.cpp.build.dir=${ARROW_HOME}/cpp/release-build/release/ -DskipTests -Dcheckstyle.skip
 # if you are behine proxy, please also add proxy for socks
-mvn clean install -P arrow-jni -am -Darrow.cpp.build.dir=../cpp/release-build/release/ -DskipTests -Dcheckstyle.skip -DsocksProxyHost=${proxyHost} -DsocksProxyPort=1080 
+mvn clean install -P arrow-jni -am -Darrow.cpp.build.dir=${ARROW_HOME}/cpp/release-build/release/ -DskipTests -Dcheckstyle.skip -DsocksProxyHost=${proxyHost} -DsocksProxyPort=1080 
 ```
 
 run test

docs/GlutenUsage.md

@@ -62,8 +62,8 @@ spark.plugins io.glutenproject.GlutenPlugin
 spark.gluten.sql.columnar.backend.lib ${BACKEND}
 spark.sql.sources.useV1SourceList avro
 spark.memory.offHeap.size 20g
-spark.driver.extraClassPath ${GLUTEN_HOME}/jvm/target/gluten-jvm-<version>-snapshot-jar-with-dependencies.jar
-spark.executor.extraClassPath ${GLUTEN_HOME}/jvm/target/gluten-jvm-<version>-snapshot-jar-with-dependencies.jar
+spark.driver.extraClassPath ${GLUTEN_HOME}/backends-velox/target/gluten-jvm-<version>-snapshot-jar-with-dependencies.jar
+spark.executor.extraClassPath ${GLUTEN_HOME}/backends-velox/target/gluten-jvm-<version>-snapshot-jar-with-dependencies.jar
 ```
 
 Below is an example of the script to submit Spark SQL query.

docs/Velox.md

@@ -1,7 +1,7 @@
 ## Velox
 
 Currently, Gluten requires Velox being pre-compiled.
-In general, please refer to [Velox Installation](https://github.com/facebookincubator/velox/blob/main/scripts/setup-ubuntu.sh) to install all the dependencies and compile Velox.
+In general, please refer to [Velox Installation](https://github.com/facebookincubator/velox/blob/main/scripts/setup-ubuntu.sh) to install all the dependencies and compile Velox. When compiling velox, it should be noted that the version of protobuf needs to be 3.13, otherwise there will be an inconsistent protobuf version when compiling Gluten with velox. 
 
 Gluten depends on this [Velox branch](https://github.com/oap-project/velox/commits/main) under oap-project.
 The changes to Velox are planned to be upstreamed in the future. Some of them have already been raised to Velox in pull requests.